Regulated fuel system



Aug. 7, 1956 P. T. NIMS REGULATED FUEL SYSTEM Filed Sept. 7. 1950 INVENTOR.

arr/75s Bic/r United States Patent 2,757,961 REGULATED FUEL SYSTEM Paul T. Nims, Detroit, Mich., assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Application September 7, 1950, Serial No. 183,555

3 Claims. (Cl. 299-58) This application relates to a regulated fuel system and more particularly to such fuel system having a plurality of bypass type nozzles which are necessarily interrelated among others in order to provide for balanced fuel consumption.

According to a feature of the invention is the provision of a balancing element among spray nozzles requiring no moving parts and repairs in service.

According to a further feature of the invention, a restriction is provided in the base of a bypass type nozzle in which the restriction element is not exposed and is free from interference and ineffectiveness due to adjustment of other parts.

According to still a further feature, a bypass type nozzle is provided in which an easily removable restriction is formed in the base in the event that plugging or other difiiculties require inspection of the restriction element.

Other features, objects, and advantages willeither be specifically pointed out or become apparent when for a better understanding of the invention reference is made to the following specification taken in conjunction with the accompanying drawings in which:

Figure 1 is a schematic piping diagram of a burner system to which the instant invention has been applied;

Figure 2 is a longitudinal section of a bypass type spray nozzle;

Figure 3 is a section of the restriction element of the spray nozzle of Figure 2; and

Figure 4 is a chart showing the operation of such a system as set forth in Figures 1 through 3.

In particular regard to Figure 1 of the drawings, a burner is arranged with a plurality of similar burners to have a bypass or return line 12 for the fuel flow not immediately consumed by the burner. Bypass line 12 feeds into a common manifold 14 for which a fuel cooler 16 may be provided, suitable connections 18 for the fuel cooler 16 providing for admission and discharge of a coolant for the heated fuel being bypassed. From cooler 16 a line 20 connects with a fitting 22 received in a bore 24 formed in a return flow control valve 26.

Control valve 26 comprises a body part 28 and a cover part 30 therefor. Suitable fasteners 32 hold cover 30 in place on the body part 28. Internally received in the body part 28 is a sleeve 34 suitably sealed at 36. A port 38 formed in sleeve 34 communicates at its outer end with an opening in registry with fitting 22 and at the inner end with an annular groove 40 formed in sleeve 34. Annular groove 40 cooperates with an externally formed annular groove 42 provided on a piston 44 slidably received in sleeve 34. A port 43 through the walls of the skirt of piston 44 establishes communication between annular groove 42 and the interior of the piston.

Received internally of the piston and engaging the piston head 46 is a spring 48 which seats at 50 on the control valve cover part 30. Adjacent spring seat 50 is a fitting 52 screwed into cover part 30. Adjacent the piston head 46 and surrounded by one or more lugs 54 Patented Aug. 7, 1956 is provided a fitting 56 received in an opening in the valve body part 28.

Fitting 56 is connected by means of a line 58 to the discharge 60 of a fuel transfer pump 62. Transfer pump 62 may be provided with a pressure-responsive bypass 64 and is connected with a fuel tank 66. By means of the pressure-responsive bypass 64, fuel pressure in pump discharge line 60 is maintained at a substantially constant value and hence the fuel pressure communicated to the control valve 26 by fitting 56 is a fairly good reference pressure.

Adapted to receive the output of pump 62 is a fuel metering device 68 which supplies a pump inlet conduit 70 for a main fuel pump 72. A bypassing line 74 establishes communication between the pump inlet 70 and the fitting 52 in the cover part 30 of control valve 26. Main pump '72 may be located in the gear case 76 of a combustion turbine 78 adjacent the accessory case 80 of the latter. Main pump 72 has a discharge 82 serving a header 84. From header 84 a plurality of nozzle intake lines 86 establish communication with bypass nozzles such as the nozzle 88 shown. The discharge side of nozzle 88 is served by the return line 12.

With respect to Figure 2 of the drawings, nozzle 88 is provided with a base 90 having a shank 91. The respective intake and discharge openings 92 and 94 in the nozzle are provided with tapped portions 93 and 95 in which suitable plugs, not shown, may be inserted. Inlet 92 communicates with an inlet passage 96 traversing shank 91 and inlet 94 communicates with a discharge passage 98 which also traverses shank 91. Inlet passage 96 communictes with a chamber 100 which communicates with tangential swirl passages 102 in the spray head of the nozzle. The spray head, having a shield 103, is generally supported by shank 91. Tangential passages 102, one or more in number, communicate with a swirl chamber 104 provided with an ejection orifice 106. The net fuel delivered by the nozzle is handled by the ejection orifice 106. Behind swirl chamber 104 is located a bypass 108 which communicates with a bypassing chamber 110 in the spray head. Bypassing chamber 110 is connected to the bypassing passage 98 in the shank 91 of the nozzle. Adjacent an end of bypassing passage 98 there is located a threaded restriction element 112.

In regard to Figure 3 of the drawings, return passage 98 has internal threading 114 for suitable reception of the external threading 116 on restriction element 112. A precalibrated restriction 118 is formed in restriction element 112 and a slot 120 is additionally provided for the proper installation and removal from passage 98 of the restriction element 112.

The overall operation of the device of Figures 1 through 3 will now be set forth. Transfer pump 62 delivers fuel from the fuel tank 66 to metering device 68. The pressure in discharge line 60 is maintained at a substantially constant value by means of the pressureresponsive bypass valve 64.

A quantity of metered fuel is delivered by metering device 68 into the inlet line 70 for main pump 72. As the metered fuel tends to accumulate in line 70, the pressure increases and the increase in-pressure is communicated through bypass line 74 to the valve control 2 6. As the pressure accumulates, the piston 44 tends to move against the constant reference preessure provided by fitting 56 and restricts the flow of fuel bypassing through line 20 through the valve control 26. A decrease in the relative pressure in line 74 will, on the other hand, permit the pressure communicated by fitting 56 to overcome the pressure internally of piston 44 and further to overcome the spring 48 to permit additional'fuel to be bypassed and the pressure restored in line 74. The valve control 26 is thus effective to maintain a substantially uniform pressure drop across the metering device 68.

Main pump 72 feeds each nozzle 88 from the common header 84. Fuel is introduced into each nozzle through the port 92 through inlet passage 96 and thence forwardly in the spray head of the nozzle to the swirl chamber 104. The fuel bypassed from swirl chamber 104 is conducted through bypass 108 into bypassing chamber 110. Fuel from chamber 110 is led through bypass passage 98 and restricting element 112 into the discharge header 14 adjacent cooler 16. From cooler 16 the cooled fuel is conducted to the control valve 26 and then bypassed into the suction line 70 for main pump 72.

The size of the restriction 118 is such that the pressure drop across the restriction will be of relatively small order compared to the pressure drops generally around the fluid system. That is to say, a satisfactory value for the pressure drop across restriction 118 has been found to be of the order of about one-quarter the pressure drop across the control valve 26 or, in reference to the pressure drop across the spray head of the nozzle 88, of the value of about one-seventh.

As respects Figure 4, a graph has been provided in order to afford a better analysis of the operation of the fuel system just set forth. The curves 122 and 124 lllustrate characteristic nozzle behavior in terms of fuel flow over a range of bypass back pressures maintained on the nozzles. In curve 122, for instance, the sum flow of fluid to the nozzle is represented by the upper part of the curve whereas the actual ejected fiow is represented by the lower part of the curve. It will be seen that for a given bypass back pressure, of the valve P, exerted on the fuel nozzle, according to the curve 122, the ejected flow is of the quantity shown at 126 and the difference between the sum fiow and the ejected flow represents the rate of fuel bypassed for any one nozzle at the supply pressure of P-|-O and the back pressure of P1. A portion, as pointed out, of the bypass back pressure is contributed by virtue of the drop across restriction element 112 and hence restriction 118 maintains the effective back pressure on an individual nozzle 88 at some predetermined level above the common pressures in cooler 16 and control valve 26.

Should one nozzle 88 of the plurality of nozzles experience a slight plug-up somewhere in its inlet line thereby causing the sum flow through the one nozzle 88 to decrease, the supply pressure effective in such nozzle is then reduced to a value such that the nozzle operation (but for the effect of the restriction 118) tends to conform in values to the curve 124 for the given back pressure F1, and it will thus be seen that the ejected flow immediately increases from the value indicated at 126 to the value indicated at 130. As a consequence and but for the effect of the restriction 118, the plugged nozzle would tend to discharge considerably more fuel than its companion normally operating nozzles which are not plugged. Reference to the back pressure P1 for curve 24 will disclose that in the nozzle the ejected flow is markedly increased for a plugged operating condition but also the bypass flow represented by the difference between the sum flow for curve 124 and the ejected flow for curve 124 is markedly decreased.

A reduction in the flow of fuel in the bypass line will of course account for a reduction in the pressure drop across the permanently open restriction element 118. The bypass back pressure across the plugged nozzle will then decrease and the overall nozzle operating conditions will necessarily change. With a decrease in the back pressure on the nozzle at the same sum fuel flow the bypass flow will tend to increase and the ejected flow will tend to decrease. When the bypass flow has increased to a point where the pressure drop across restriction element 118 has tended to stabilize operation of the plugged nozzle itself, the plugged nozzle may be presumed to have stabilized in conformity with the curve 124 at the back pressure indicated at P2 in Figure 4.

In such circumstances at the reduced supply pressure P indicated for curve 124, the ejected flow will assume a magnitude as is indicated at 138, which roughly equals the magnitude 126 shown originally for the nozzle before it was plugged. In curve 124 the difference between the sum flow and the ejected flow 138 is equal to the bypass quantity 136, the fiow of which causes the appropriate reduced pressure drop across restriction orifice 112. It will be appreciated then that the plugged nozzle has by virtue of the permanently open restriction at the base thereof been caused to balance up as far as the ejected fuel output for the remainder of the normally operating nozzle is concerned. Hence no tube failures in the burner will result since the net fuel flow is selfbalanced.

It is to be appreciated that for a given sum fiow of fuel the gains in the rate of bypass flow are made at the expense of ejected flow and vice versa. In order to reduce the ejected flow, the bypass flow must be increased. It should be observed that as the sum flow of fuel is decreased due to a plugging or other artificial restriction, the rate of ejected flow tends to increase to a marked degree. The instant improvement compensates for such tendency and by use of no moving parts.

The regulation of the bypass back pressure for any individual nozzle is regulated solely by its associated restricting orifice. During the operation of the fuel systern under any 'given set of operating conditions the bypass pressure for any given nozzle is maintained constant. Therefore, as the return flow on the upstream side of any individual restriction decreases, the pressure drop across that orifice decreases. But since the back pressure on the downstream side of the orifice remains the same, a reduction in pressure drop across that individual orifice results in a lower back pressure on the upstream side of the orifice. Thus, having reference again to Figure 4, the bypass back pressure will drop from some value P1 to a lower value P2.

Variations within the spirit and escope of the invention described are equally comprehended by the foregoing description.

What is clairned is:

1. A fuel circuit including a pair of bypass-type ejection nozzles connected in parallel, a common pump for transferring fuel from a source under pressure to said nozzles, and a common bypass control valve connected to the nozzles and to the intake of the pump for con ducting bypassed fuel from the former to the latter at a relative reduction in pressure, each nozzle of said pair incorporating means in the bypass thereof forming a permanent restriction ahead of said common control valve and normally providing a pressure drop thereacross substantially equal to one-fourth of the bypass pressure drop across the common control valve such that when the plugging of the inlet of the other nozzle causes the bypass flow rate of the same through its restriction to be reduced, the back pressure on said other nozzle is likewise reduced causing the ejected output operation of the said other nozzle to remain substantially constant.

2. In a fuel ejection system for a combustion apparatus, a plurality of return flow nozzles, each nozzle including a fuel ejection head for ejecting fuel, individual fuel supply and return conduits communicating with each nozzle ejection head, each of said individual supply conduits being effective to accommodate the fiow of fuel to the associated ejection head While the return conduit therefor conducts fuel from the same, the rate of fuel flow in the individual return conduit for any one nozzle being equal to the difference between the flow in the individual supply conduit associated therewith and the ejection flow therefrom, a common fuel return conduit and a common fuel supply conduit connected to each of said individual return conduits and each of said individual supply conduits respectively, each of said nozzles having a flow regulating element received in the individual return conduit thereof, each flow regulating element being formed with a permanently open precalibrated orifice for maintaining a predetermined pressure difierential thereacross for a given rate of flow therethrough, a fuel metering mechanism located in said common fuel supply conduit for scheduling a flow of fuel to said nozzles at a rate determined by the fuel requirements for said combustion apparatus, and pressure regulator valve means having portions located in said common return conduit for maintaining a predetermined pressure differential across said fuel metering mechanism, the calibration of said orifice being a function of the pressure drop across one of said nozzles and the pressure drop across said pressure regulator valve means, the change in pressure differential across said flow regulating element accompanying a given reduction in the fuel supply flow rate to one of said nozzles being of a sufficient magnitude to maintain the ejection flow rate for said one nozzle at a substantially constant value.

3. In a fuel system for combustion apparatus, a plurality of return flow nozzles, each nozzle including a fuel spray head with a fuel ejection orifice for ejecting fuel, individual fuel supply and return conduits communicating with said spray head, each of said supply conduits being effective to conduct fuel to the associated spray head while the return conduit therefor conducts fuel from the same, the fuel flow in the return flow conduit for any one nozzle being equal to the difference between the flow in the supply conduit associated therewith and the ejection flow therefrom, a common return conduit connected to each of said individual return conduits, at least one of said nozzles having a removable element received in the individual return conduit thereof, said element being formed with a permanently open precalibrated orifice for maintaining a predetermined pressure differential thereacross, the magnitude of said pressure differential being equal to approximately one-seventh the magnitude of the pressure drop across the spray head for said one nozzle, said orifice tending to maintain the fuel ejection flow rate for said one nozzle at a substantially constant value upon a decrease in the fuel pressure in the individual fuel supply conduit for said one nozzle.

References Cited in the file of this patent UNITED STATES PATENTS 1,628,424 Peabody May 10, 1927 1,824,952 Graham Sept. 29, 1931 2,079,430 Bargeboer May 4, 1937 2,263,913 Bargeboer Nov. 25, 1941 2,315,172 Voorheis Mar. 30, 1943 2,374,041 Saha Apr. 17, 1945 2,436,815 Lum Mar. 2, 1948 2,537,681 Lawrence Jan. 9, 1951 2,599,680 Weeks June 10, 1952 2,604,149 Wynne July 22, 1952 2,606,066 Thompson Aug. 5, 1952 2,619,163 Wynne NOV. 25, 1952 2,622,610 Rowe Dec. 23, 1952 2,656,848 Noon Oct. 27, 1953 2,706,520 Chandler Apr. 19, 1955 FOREIGN PATENTS 577,132 Great Britain May 7, 1946 

